Mr Ford was justice minister in the devolved executive from 2010 to 2016.

“Complaints about ‘unfair justice system’ are utterly wrong and come very close to political interference.

“I hope the Police Service of Northern Ireland (PSNI) and the Public Prosecutions Service Northern Ireland tell the Prime Minister to get off their turf.”

PSNI figures previously obtained by the BBC suggested investigations into killings by the Army account for about 30% of the PSNI’s legacy workload, with the remainder concerning republicans or loyalists.

It is investigating more than 1,000 deaths not previously fully reviewed.

MPs had urged a statute of limitations which would prevent anyone from facing trial for offences that happened during the conflict, including former servicemen and paramilitaries.

But such a law is not expected to feature in Government proposals for addressing Northern Ireland’s toxic past and the DUP has said that a new law covering a number of wars and conflicts should be kept separate from the legacy suggestions in case IRA offenders pressed for an amnesty.

What's up with T May? Surely an exHomeSec should know police & prosecutors follow the evidence regardless. Complaints about "unfair justice system" are utterly wrong and come very close to political interference. I hope @PoliceServiceNI and PPSNI tell PM to get off their turf.

Senior members of the Cabinet including Defence Secretary Gavin Williamson are among those understood to have expressed concern at any proposals on addressing the past which did not seek to prevent soldiers from being prosecuted.

Over the last year, the concept of an amnesty has gained traction among a number of Westminster backbenchers, who claim recent prosecutions of former British soldiers are tantamount to a “witch-hunt”.

Prosecutors and police in Northern Ireland insist such allegations simply do not stand up to scrutiny, with a breakdown of figures showing no disproportionate focus on ex-security force members.

Mechanisms to deal with the conflict legacy were agreed by Northern Ireland politicians in the 2014 Stormont House Agreement; an amnesty was not among them.

The agreed proposals, including a new independent investigatory unit, a truth recovery body and an oral archive, are on ice due to a small number of outstanding disputes.

DUP Lagan Valley MP Sir Jeffrey Donaldson said a statute of limitations for the armed forces should also cover conflicts such as Iraq and Afghanistan.

Sinn Fein’s Northern Ireland leader Michelle O’Neill has said victims should not be held to ransom by Tory party in-fighting.

The PSNI figures appeared to contradict Mrs May’s claim in the House of Commons on Wednesday that “the only people being investigated” were former members of the armed forces and those who served in law enforcement in Northern Ireland, while “terrorists are not being investigated”.

Asked about the apparent discrepancy, the Prime Minister’s official spokesman told a regular Westminster media briefing: “The Prime Minister was clear that she believes the current arrangements are unfair and that the current situation is disproportionate, if you look at the fact that 90% of the killings which took place during the Troubles involved terrorists.

“I think the point she was making is that the current system is not fair and it’s not proportionate.”